1. Field of the Invention
This invention relates to a liquid ejection recording head, and more particularly to a liquid ejection recording head, particularly an ink jet recording head, in which liquid flow path walls formed of a hardened film of photosensitive resin and/or walls surrounding a liquid chamber are formed on the surface of a substrate on which liquid discharge energy generating elements are installed and a lid plate is provided on top thereof.
2. Description of the Prior Art
A liquid ejection recording head applied to the ink jet recording system is generally provided with minute ink discharge ports (orifices), ink paths and ink discharge energy generating portions provided in a part of the ink paths.
As a method of making such a conventional ink jet recording head, there is known, for example, a method of forming minute grooves in a support member of glass or metal by cutting or etching, thereafter joining the support member formed with the grooves to another suitable plate and forming ink paths.
However, in the head made by such a method, the roughness of the inner wall surfaces of the liquid paths worked by cutting is too great or distortion is created in the liquid paths due to variations in etching rate and thus, it is difficult to obtain liquid paths of a constant path resistance and irregularity is liable to occur to the ink discharge characteristic of the recording head during its use. Also, during the cutting work, breakage or planing of the plate is liable to occur and therefore, the yield of manufacture is low and on the other hand, when effecting the etching work, there are involved a number of manufacturing steps, which results in an increased cost of manufacture.
Further, a disadvantage common to the conventional methods is that when a grooved plate formed with liquid flow paths is to be cemented to a plate provided with driving elements such as electro-mechanical converting members (for example, piezo-electric elements) or electro-thermal converting members (for example, heat generating elements) as ink discharge energy generating elements which generate the energy acting on ink to eject the ink from the orifices and form flying droplets, it is difficult to align these plates and this is unsuitable for mass production.
So, as a liquid ejection recording head constructed to overcome these disadvantages, a liquid ejection recording head in which liquid flow path walls formed of a photosensitive resin hardening film are formed on a substrate on which ink discharge energy generating elements are disposed and a lid plate is provided on the flow paths is proposed, for example, by Japanese Laid-Open Patent Application No. 43876/1982.
This liquid ejection recording head made by the utilization of photosensitive resin is excellent in solving the disadvantages peculiar to the conventional heads that the finish accuracy of the liquid flow paths is low, that the manufacturing steps are complicated and that the yield of manufacture is low.
FIGS. 1 and 2 of the accompanying drawings show two forms of such a conventional liquid ejection recording head. In these Figures, reference numeral 1 designates a support member formed of glass, ceramics, plastics or a metal. Reference numeral 2 denotes a plurality of (nine in the case of the present example) liquid discharge energy generating elements disposed on the support member 1. As the discharge energy generating elements 2, use is made of heat generating elements or piezo-electric elements. Wiring for signal inputting, not shown, is connected to these elements 2. In the case of the heat generating elements, the liquid near the elements in liquid flow paths 3 in which individual elements 2 are provided is sharply heated, whereby the energy for discharging the ink is generated and the ink is discharged from discharge ports 4 formed at the end of the flow paths 3.
Also, where the discharge energy generating elements 2 are piezo-electric elements, the discharge energy for discharging the ink is likewise generated by mechanical vibration of these elements, whereby discharge of the ink can be accomplished.
Reference numeral 5 designates a liquid chamber communicating with the individual liquid flow paths 3. A surrounding wall 6B is formed around the liquid chamber 5, and flow path walls 6A are formed between the flow paths 3. The surrounding wall 6B and flow path walls 6A may be formed of a photosensitive resin hardening film by photolithography, i.e., photoengraving.
A lid plate 7 is mounted on the substrate 1 on which the flow paths 3 and liquid chamber 5 are formed in this manner. The lid plate 7 is generally formed of glass, ceramics, plastics or a metal and, for example, a photosensitive resin layer 8 is formed on the joined surface of the lid plate 7.
The formation of such a layer 8 may be achieved by applying photosensitive resin liquid to the lid plate 7 by the spinner coating method or by laminating photosensitive resin dry films on the lid plate 7. Designated by 9 are liquid supply ports formed in the lid plate 7. Thus, a recording head 10 is provided by joining the lid plate 7 formed with the photosensitive resin layer 8 and supply ports 9 to the upper surfaces of the surrounding wall 6B and flow path walls 6A.
The example shown in FIG. 1 and the example shown in FIG. 2 are similar to each other with the exception that they differ in the shape of a part of the surrounding wall 6B and flow path walls 6A, and the liquid ejecting operation in the recording head 10 provided in this manner is generally known and therefore need not be described.
However, in the conventional recording head made by the utilization of such photosensitive resin, when adhesively securing the flow path walls 6A formed of a photosensitive resin hardening film and the wall 6B for ink reservoir connected to the flow path walls to the lid plate of hardening film, it has been technically difficult to bring them into completely intimate contact with each other over the entire joined surface thereof and therefore, specifically, the procedures as described below have been resorted to.
(1) Uniformly applying an epoxy adhesive agent or an acrylic adhesive agent to a thickness of 3-4 .mu.m to the joined surface of the lid plate formed of a material such as glass, ceramics, a metal or plastics, by the spinner coating method and joining it to the upper surface of the wall of photosensitive resin hardening film, thereby hardening said adhesive agent;
(2) Spinner-coating the joined surface of the lid plate 7 with said adhesive agent, and then preliminarily heating the adhesive agent to make it into B-stage, and joining the lid plate to the upper surface of the walls formed of a photosensitive resin hardening film, thereby essentially hardening said adhesive agent;
(3) Directly thermally fusing the lid plate 7 formed of a thermoplastic resin material such as acrylic resin, ABS resin or polyethylene to the upper surface of the walls of the photosensitive resin hardening film; and
(4) Sticking a photosensitive resin layer to the joined surface of said lid plate, joining it to the upper surface of the walls of said photosensitive resin hardening film, and applying a light thereto, thereby hardening the same.
However, with any of the procedures as described above, bubbles may remain on the joined surface between the upper surface of the walls formed of the photosensitive resin hardening film and the lid plate 7. Also, when the two joined members are strongly pressed against each other to bring them into intimate contact with each other, the adhesive agent and the photosensitive resin provided on the joined surface of the lid plate 7 will protrude into the liquid flow paths 4 to clog the liquid flow paths 4, and this has left a problem as to the reliability of the joined surface.
Also, even when the adhesion has been done completely, stress and distortion have been created by the difference in adhesion strength resulting from the difference in area of adhesion, and this has sometimes led to the occurrence of peeling-off of the lid plate or distortion of the recording head.